Conventionally, a sewing machine is known that can adjust amplitude of swing movement of a needle bar by switching operation when a sewing operation is at rest. This sewing machine has a bed portion, a column leg portion erecting from a right end of the bed potion, and an arm extending in a leftward direction to be in opposing to the bed portion. The bed portion is equipped with a feed dog for feeding a cloth, the needle bar to which a needle can be mounted at a head of the arm portion, a start and stop switch for ordering of starting and stopping the sewing operation, and a display showing various types of utility patterns or a variety of embroidery patterns, function names and more. In addition, an electronic sewing machine is disclosed in which the right side of the column leg portion is equipped with a connector jack to which a connecting cord plug of a foot controller is connected (refer to, for example, Patent Document 1). This sewing machine can change the amplitude amount of swing movement of the needle bar by user's switching operation when the user stops the sewing operation. Furthermore, this sewing machine comprises a foot controller having a variable resistor. User's by-foot depression of the foot controller is capable of ordering a microcomputer to start the sewing operation. Depending on an amount of the depression of the foot controller, a sewing speed is adjusted which is indicated by an elevating speed of the needle.
In addition, a sewing machine which includes a sewing machine motor, a speed control drive controlling the sewing machine motor, a speed command unit (foot controller) supplying a speed command signal to the speed control part, and more is disclosed (refer to, for example, Patent Document 2). When a user depresses a pedal of the speed command unit, a resistive value of a variable resistor changes which is provided in the pedal. And the speed command unit receives a speed command voltage, as the speed command signal, which depends on the resistive value and performing a driving control of the sewing machine in depending on the speed command voltage.    1: Patent Document 1: Japanese Unexamined Patent Publication No. 2006-34675    2: Patent Document 2: Japanese Unexamined Patent Publication Sho55-71186